The other problem with cloud storage is YOUR upload speed cap, and how long it will take to upload the files.
If you shoot an event/gig of say 500 pix at 20MB average file size = 10,000MB = 10 GB total size to upload (if my math is correct).
At a 6Mb (bits) per sec (0.6MB) upload speed that is 16,667 seconds.
There is overhead involved with processing each file, so lets add 1 sec per file, total 500 seconds, and we are at 17,167 seconds = 4.8 hours.
This makes it an overnight backup process.
WARNING: Note the upload time above. On your initial backup, you would probably be loading a few hundred GB, or more, of files. Using the above math, 100GB = 48 hours (2 days), 200GB = 96 hours (4 days), 400GB = 192 hours (8 days)
My friend uses iDrive. To avoid the initial backup taking DAYS/WEEKS. They have an option to jump start the backup, where they sent him an external drive, for him to backup to, and ship back to them. Then they load the drive into their system, then nightly online backup does the incremental backups.
What makes sense to me, is to use a hybrid of online/cloud backup for daily backups + periodic full backup to HD.
By periodic, I mean every week/month/quarter (whatever time period is appropriate for YOU) and after any significant gig/event.
A full backup takes longer, but IMHO is easier for a home operation than base + incrementals.